CVE-2021-20801Network attack vector

Authenticated data disclosure via XML external entities

Published Oct 13, 2021 · Updated Aug 3, 2024

XML external entity injection in Cybozu Remote Service 3.1.8 through 3.1.9 allows remote authenticated users to read stored data. Cybozu identifies the affected function only as general and has not disclosed which request parses attacker-controlled XML or how external entity resolution remains enabled. Exploitation requires an authenticated network session and, according to the CNA record, Mozilla Firefox; the bounded result is unauthorized reading of product-stored information.

CVSS severity4.3
Medium
EPSS probability1.06%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

XML external entity injection in Cybozu Remote Service 3.1.8 through 3.1.9 allows remote authenticated users to read stored data. Cybozu identifies the affected function only as general and has not disclosed which request parses attacker-controlled XML or how external entity resolution remains enabled. Exploitation requires an authenticated network session and, according to the CNA record, Mozilla Firefox; the bounded result is unauthorized reading of product-stored information.

The record

CVE
CVE-2021-20801
Published
Oct 13, 2021
Updated
Aug 3, 2024
Vendor
Cybozu
Product
Cybozu Remote Service
Classifications
CWE-611
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 13, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.1.8 to 3.1.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Cybozu · Cybozu Remote Serviceversion=3.1.8 to 3.1.9

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.3JPCERT/CCCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
4.0JPCERT/CCAV:N/AC:L/Au:S/C:P/I:N/A:N
4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-611Improper Restriction of XML External Entity Reference

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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